Stacked chip package structure with leadframe having bus bar

ABSTRACT

The present invention provides a chip-stacked package structure with leadframe having bus bar, comprising: a leadframe composed of a plurality of inner leads arranged in rows facing each other, a plurality of outer leads, and a die pad, wherein the die pad is provided between the plurality of inner leads and is vertically distant from the plurality of inner leads; a chip-stacked structure formed with a plurality of chips that stacked together and set on the die pad, the plurality of chips and the plurality of inner leads being electrically connected with each other; and an encapsulant covering over the chip-stacked package structure and the leadframe, in which the leadframe comprises at least a bus bar, which is provided between the plurality of inner leads arranged in rows facing each other and the die pad.

This application is a continuation application of, and claims a priorityto the U.S. patent application Ser. No. 11/826,415 filed on Jul. 16,2007, now U.S. Pat. No. 7,786,595 which claims a priority to the foreignpatent application in Taiwan with a serial number TWO95133670, filed onSep. 12, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an offset chip-stacked packagestructure, and more particularly, to an offset chip-stacked structurewith leadframe having bus bar.

2. Description of the Prior Art

In semiconductor post-processing, many efforts have been made forincreasing scale of the integrated circuits such as memories whileminimizing the occupied area. Accordingly, the development ofthree-dimensional (3D) packaging technology is in progress and the ideaof making up a chip-stacked structure has been disclosed.

The prior art has taught that a chip-stacked structure can be formed byfirstly stacking a plurality of chips and then electrically connectingthe chips to the substrate in a wire-bonding process. FIG. 1A is across-sectional view of a prior chip-stacked package structure stackedby chips of same or similar size. As shown in FIG. 1A, a conventionalchip-stacked package structure 100 includes a package substrate 110,chips 120 a and 120 b, a spacer 130, wires 140, and an encapsulant 150.The package substrate 110 has a plurality of pads 112 thereon, and thechips 120 a and 120 b are also respectively provided with the pads 122 aand 122 b arranged in peripheral type. The chip 120 a is provided on thesubstrate 110, while the chip 120 b is provided on the chip 120 a with aspacer 130 intervened there-between. The chip 120 a is electricallyconnected to the substrate 110 by bonding two ends of one of the wires140 to the pads 112 and 122 a respectively. The chip 120 b iselectrically connected to the substrate 110 in similar manner. Theencapsulant 150 is then provided on the substrate 110 to cover the chips120 a and 120 b and the wires 140.

Since the pads 122 a and 122 b are respectively provided at theperipheral of the chip 120 a and the 120 b, there is a need to apply thespacer 130 to prevent the chip 120 b from directly contacting with thechip 120 a for performing the subsequent wire-bonding. However, the useof spacer 130 increases the thickness of the chip-stacked packagestructure 100.

Another prior chip-stacked package structure for different-sized chipshas been disclosed. Referring to FIG. 1B, another conventionalchip-stacked package structure 10 includes a package substrate 110,chips 120 c and 120 d, wires 140, and an encapsulant 150. The substrate110 has pads 112 on it. The chip 120 c is larger than the chip 120 d insize. The chips 120 c and 120 d are respectively provided withperipherally arranged pads 122 c and 122 d. The chip 120 c is providedon the substrate 110 while the chip 120 d is provided on the chip 120 c.The chip 120 c is electrically connected to the substrate 110 by bondingtwo ends of one of the wires 140 to the pads 112 and 122 c respectively.The chip 120 d is electrically connected to the substrate 110 in similarmanner. The encapsulant 150 is then provided on the substrate 110 tocover the chips 120 c and 120 d and the wires 140.

Since the chip 120 d is smaller than the chip 120 c, the chip 120 dwould not covered over the pads 122 c of the chip 120 c when the chip120 d is stacked on the chip 120 c. However, the condition that theupper chip must have size smaller than that of the lower chip limitsnumber of the chips to be stacked in the chip-stacked package structure10.

In other words, the above-mentioned chip-stacked package structures havedrawbacks of either increasing thickness as shown in FIG. 1A or limitingnumber of the chips to be stacked as shown in FIG. 1B.

SUMMARY OF THE INVENTION

In view of the drawbacks and problems of the prior chip-stacked packagestructure as mentioned above, the present invention provides athree-dimensional chip-stacked structure for packaging multi-chips withsimilar size.

It is an object of the present invention is to provide a leadframestructure provided with bus bar for offset chip stacking and packagingand so as to the package has higher density and thinner thickness.

It is another object of the present invention to provide an offsetchip-stacked structure for packaging with a leadframe that having busbar structure and so as to make the circuit design more flexible andgain higher reliability.

According to abovementioned objects, the present invention provides anoffset chip-stacked package structure with leadframe having bus bar,comprising: a leadframe composed of a plurality of inner leads arrangedin rows facing each other, a plurality of outer leads, and a die pad,wherein the die pad is provided between the plurality of inner leads andis vertically distant from the plurality of inner leads; a plurality ofstacked semiconductor chip structures being misaligned for forming anoffset chip-stacked structure on the die pad, the plurality of chips onthe offset chip-stacked structure and the plurality of inner leads beingelectrically connected with each other; and an encapsulant covering theplurality of semiconductor chip structures and the leadframe; whereinthe leadframe comprises at least a bus bar, which is provided betweenthe plurality of inner leads arranged in rows facing each other and thedie pad.

The present invention then provides an offset chip-stacked packagestructure with leadframe having bus bar, comprising: a leadframecomposed of a plurality of outer leads, a plurality of inner leadsarranged in rows facing each other, and a die pad, wherein the die padis provided between the plurality of inner leads and is verticallydistant from the plurality of inner leads; a plurality of offsetchip-stacked structures set on the die pad and electrically connected tothe plurality of inner leads arranged in rows facing each other; and anencapsulant covering the plurality of offset chip-stacked structures andthe leadframe, the plurality of outer leads extending out of theencapsulant; wherein the leadframe comprises at least a bus bar providedbetween the plurality of inner leads and the die pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to 1B are diagrams schematically showing a conventionalchip-stacked package structure.

FIG. 2A is a top-elevational view schematically showing the chip-stackedstructure according to the present invention.

FIG. 2B is a cross-sectional view schematically showing the chip-stackedstructure according to the present invention.

FIGS. 2C to 2E are cross-sectional views schematically showing theoffset chip-stacked structure according to the present invention.

FIGS. 3A to 3C are diagrams schematically showing the redistributionlayer formed in a process according to the present invention.

FIGS. 4A to 4B are cross-sectional views schematically showing thebonding area on the redistribution layer according to the presentinvention.

FIGS. 5A to 5C are cross-sectional views schematically showing an offsetchip-stacked structure with redistribution layer according to thepresent invention.

FIGS. 6A to 6B are top-elevational views schematically showing an offsetchip-stacked package structure according to the present invention.

FIGS. 7A to 7B are top-elevational views schematically showing an offsetchip-stacked package structure according to another embodiment of thepresent invention.

FIGS. 8A to 8B are top-elevational views schematically showing an offsetchip-stacked package structure according to another embodiment of thepresent invention.

FIG. 9 is a cross-sectional view schematically showing an offsetchip-stacked package structure according to the present invention.

FIG. 10 is a cross-sectional view schematically showing an offsetchip-stacked package structure according to an embodiment of the presentinvention.

FIG. 11 is a cross-sectional view schematically showing an offsetchip-stacked package structure according to another embodiment of thepresent invention.

FIG. 12 is a cross-sectional view schematically showing an offsetchip-stacked package structure according to another embodiment of thepresent invention.

FIG. 13 is a cross-sectional view schematically showing an offsetchip-stacked structure according to another embodiment of the presentinvention.

FIG. 14 is a cross-sectional view schematically showing an offsetchip-stacked structure according to another embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsare shown. In the following, the well-known knowledge regarding thechip-stacked structure of the invention such as the formation of chipand the process of thinning the chip would not be described in detail toprevent from arising unnecessary interpretations. However, thisinvention will be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein.

According to the semiconductor packaging process, a Front-End-Processexperienced wafer is performed a thinning process to reduce thethickness to a value between 2 mil and 20 mil, and then the polishedwafer is applied with a polymer material such as a resin or a B-Stageresin by coating or printing. Next, a post-exposure baking or lightingprocess is applied to the polymer material so that the polymer materialbecomes a viscous semi-solidified gel-like material. Subsequently, aremovable tape is attached to the gel-like material with capable ofviscous semi-solidified, and then the wafer is sawed into chips or dies.At last, these chips or dies are stacked on and connected to a substrateto form a chip-stacked structure.

Referring to FIGS. 2A and 2B, a chip 200 experiencing theabove-mentioned processes has an active surface 210 and a back surface220 in opposition to the active surface 210 with an adhesive layer 230that is formed on the back surface 220. It is to be noted that theadhesive layer 230 is not limited to the above-mentioned semi-solidifiedgel-like material and can be any adhesive material, such as die-attachedfilm, for joining the chip 200 and a substrate together. Moreover, theactive surface 210 is thereon provided with a plurality of pads 240arranged along a side edge. Accordingly, an offset chip-stackedstructure 30 as shown in FIG. 2C can be formed. The offset chip-stackedstructure 30 is a ladder-like structure formed by aligning the side edgeof upper chips with the edge line 260 of the bonding area 250 on lowerchips. The edge line 260 herein is a presumed line for reference onlybut not a line exists on chip 200.

Referring to FIG. 2D, the uppermost chip of the structure 30 can furtherhave same pads as the pads 240 on the other side for providing moreconnections with the substrate. Referring to FIG. 2E, the uppermost chipof the structure 30 can have size smaller than that of the lower one.The arrangement of the pads 240 or the size of the chips describedherein is for embodying but not limiting the invention. Any chip-stackedstructure satisfying the above-mentioned statement would be regarded asan aspect of the invention.

Referring to FIGS. 3A to 3C, the process of making a chip with aredistribution layer is disclosed. According to the present invention,the redistribution layer (RDL) is formed with a plurality of padsprovided on one side edge of the chip and the details are described asfollows.

As shown in FIG. 3A, the chip 310 has first pads 312 a and second pads312 b on the active surface and along side edges. The first pads 312 aare located inside a bonding area 320, while the second pads 312 b arelocated outside the bonding area 320. As shown in FIG. 3B, a firstpassivation layer 330 with a plurality of first openings 332 forexposing the first pads 312 a and the second pads 312 b is first formedon the chip 310, and a redistribution layer 340 with a plurality ofconductive wires 342 and a plurality of third pads 344 is then formed onthe first passivation layer 33. The third pads 344 are located insidethe bonding area 320 and the plurality of conductive wires 342 that iselectrically connected to the second pads 312 b and the third pads 344.The redistribution layer 340 is made up of conductive materials such asgold, copper, nickel, titanium tungsten, titanium or others. As shown inFIG. 3C, the chip structure 300 is completed by forming a secondpassivation layer 350 with a plurality of second openings 352 on theredistribution layer 340 to cover the area rather than the first pads312 a and the third pads 344 but expose the first pads 312 a and thethird pads 344.

It is to be noted that the first pads 312 a and the second pads 312 bcan be arranged on the surface of the chip 310 not only in theabove-mentioned peripheral type but also in an area array type or othertypes rather than the above-mentioned types, provided that the secondpads 312 b are electrically connected with the third pads 344 via theconductive wires 342. Moreover, the third pads 344 can be arranged in amanner of being along side edge of the chip 310 and in parallel to thepads 312 a such as shown in FIG. 3B or other manners provided that thethird pads 344 are located inside the bonding area 320.

Referring now to FIGS. 4A and 4B, show the cross-section views drawnalong section lines A-A′ and B-B′. As shown in FIGS. 4A and 4B, thewhole chip structure 300 is composed of the chip 310 and theredistribution layer 400. The redistribution layer 400 is composed offirst passivation layer 330, redistribution layer 340, and secondpassivation layer 350. The presumed bonding area 320 of the chip 310 isa side edge adjacent to the chip 310. Moreover, the chip 310 has aplurality of first pads 312 a and second pads 312 b, wherein the firstpads 312 a are inside the bonding area 320 and the second pads 312 b areoutside the bonding area 320.

The first passivation layer 330 disposed on the chip 310 has a pluralityof first openings 332 to expose these first pads 312 a and second pads312 b. The redistribution layer 340 with a plurality of third pads 344is disposed on the first passivation layer 330 and extends from secondpads 312 b to presumed bonding area 320, where the third pads arelocated. The second passivation layer 350 covers the redistributionlayer 340 and expose first pads 312 a and third pads 344 through aplurality of second openings 352. Since the first pads 312 a and thirdpads 344 are in the presumed bonding area 320, the area rather than thebonding area 320 on the second passivation layer 350 is capable ofcarrying another chip structure and therefore accomplishing an offsetchip-stacked structure.

Referring to FIG. 5, shows an offset chip-stacked structure 50 of thepresent invention. An offset chip-stacked structure 50 includes aplurality of stacked chips 500. Each of the chips 500 is formed with aredistribution layer 400 so that each of the chips 500 can be providedwith pads inside the bonding area 320 on each chip. In this way, theoffset chip-stacked structure 50 is formed by aligning the side edge ofupper chips with a presumed edge line of the bonding area 320 on lowerchips and an adhesive layer 230 formed by a polymer material is used toconnect any two chips among the plurality of chips 500. Moreover, asshown in the present embodiment in FIG. 5B, the uppermost chip of theoffset chip-stacked structure 50 can further have same pads as the pads312 on the other side for providing more connections with the substrateand the method for forming this kind of structure is as shown in FIG. 4.Referring to FIG. 5C, the uppermost chip of the offset chip-stackedstructure 50 can have size smaller than that of the lower one. Thearrangement of the pads 312 and 344 or the size of the chips 500described herein is for embodying but not limiting the invention. Anychip-stacked structure satisfying the above-mentioned statement would beregarded as an aspect of the invention. For example, each of the chips500 can be formed with bonding areas that are not only on the right sideas shown in FIGS. 5A to 5B but also on the left side.

In the following, two offset chip-stacked structures each connected withleadframes according to the present invention will be disclosed, inwhich the above-mentioned offset chip-stacked structure 50 will be takenas an example for illustration. However, the following descriptions canalso be applied to the above-mentioned offset chip-stacked structure 30.

Referring to FIGS. 6A and 6B, shows the plane views of a chip-stackedpackage structure of the present invention. As shown in FIGS. 6A and 6B,the chip-stacked package structure comprises a leadframe 600 and anoffset chip-stacked structure 50, wherein the leadframe 600 is composedof a plurality of inner leads 610 arranged in rows facing each other, aplurality of outer leads (not shown), and a die pad 620. The die pad 620is provided between the plurality of inner leads 610 and is verticallydistant from the plurality of inner leads. In the present embodiment,the offset chip-stacked structure 50 is fixedly connected to the die pad620 with an adhesive layer 230. The adhesive layer 230 in the presentinvention is not limited to the above-mentioned semi-solidified gel-likematerial and can be any adhesive material, such as die attached film,for joining the offset chip-stacked structure 50 and the die pad 620together. Then metal wires 640 are provided for connecting chip-stackedstructure 50 and the inner leads 610 of leadframe 600.

Then, referring to FIGS. 6A and 6B, the leadframe 600 of chip-stackedpackage structure of the present invention further comprises at least abus bar 630 provided between the die pad 620 and the plurality of innerleads 610 arranged in rows facing each other, wherein the bus bar 630can be arranged in a stripe-shaped configuration, as shown in FIGS. 6Aand 6B; meanwhile, the bus bar 630 can also be arranged in a ring-shapedconfiguration, as shown in FIGS. 7A and 7B. Moreover, as what isdescribed above, the pads 312/344 in the bonding area 320 of chip 500can be arranged in single row, as shown in FIGS. 6 and 7, or two rows,as shown in FIGS. 8A and 8B, and is not limited in the presentinvention.

The description will go to the part of using the bus bar 630 toaccomplish jumping connections of metal wires 640, referring to FIG. 6A.Referring again to FIG. 6A, the pad with letter “b” and the pad withletter “b′” on the chip 500 are connected to the inner lead 6103 and theinner lead 6123 respectively. Apparently, the bus bar 6301 and the busbar 6302 can be served as transferring pads for making jumpingconnections between the pads with letter “b” and with “b′” and the innerleads 6103 and 6123 and thus the metal wires 640 would not cross eachother. For example, a metal wire 640 has its one end connected to thepads with letter “b” and with “b′” on chip 500 and the other endconnected to the bus bars 6301 and 6302; then another wire 640 has itsone end connected to the bus bars 6301 and 6302 and the other endconnected to the inner leads 6103 and 6123. Thus, the connection betweenthe pads with letter “b” and with “b′” and the inner leads 6103 and 6123can be made without crossing the wire connecting the pad with letter “c”and the inner lead 6102. And in another embodiment, as shown in FIG. 6B,the jumping connection of two pads on chip 500 can be accomplished witha plurality of bus bar structures 630. Referring to FIG. 6B, the padswith letter “a” and with “c′” on chip 500 are connected to the innerleads 6103 and 6101. The bus bar 6301 can be served as a transferringpad for the pad with letter “a”. A metal wire 640 first connects the padwith letter “a” and the bus bar 6301, and another metal wire 640connects the bus bar 6301 and the inner lead 6103. The bus bar 6302 canbe served as a transferring pad for the connection between the pad withletter “c” and the inner lead 6101 with a metal wire 640. Moreover, onanother side of the leadframe 600, the bus bar 6303 can be served as atransferring pad for the pad with letter “b′”. A metal wire 640 connectsthe pad with letter “b′” and the bus bar 6303, and another metal wire640 connects the bus bar 6303 and the inner lead 6123. Consequently, thebus bars 630 in the leadframe 600 according to the present inventionprovides a plurality of transfer pads for jumping connections to preventmetal wires from crossing each other and avoid unnecessary short.Meanwhile, the bus bars 630 make the circuit design more flexible andraise the reliability in package processing. The connection of metalwires can also be performed in the embodiments in FIGS. 7 and 8according to the structure of bus bars 630.

It is to be noted that the offset chip-stacked structure 50 is set onthe leadframe 600 and the chips 500 can be that having same size andperforming same function such as memory chips or chips having differentsizes and performing different functions such as the case shown in FIGS.2E and 5C (the chips on the uppermost layer being drive chips and therest being memory chips). The detailed description for size and functionof these chips is omitted hereinafter.

Referring to FIG. 9, which is a cross-sectional view of the offsetchip-stacked package structure in FIG. 6A drawn along section line A-Aor in FIG. 7A drawn along section line B-B. As shown in FIG. 9, theleadframe 600 and the offset chip-stacked structure 50 are connectedwith a plurality of metal wires 640, wherein the leadframe 600 iscomposed of a plurality of inner leads 610 arranged in rows facing eachother, a plurality of outer leads (not shown), and a die pad 620. Thedie pad 620 is provided between the plurality of inner leads 610 and isvertically distant from the plurality of inner leads 610, at least a busbar 630 being provided between the inner leads 610 and the die pad 620.In the present embodiment, the bus bar 630 and the die pad 620 arevertically at the same height. The metal wire 640 a has one endconnected to the first pad 312 a or third pad 344 of the chip 500 a(first pad 312 a or third pad 344 described in FIG. 3 for example) andhas the other end connected to the first pad 312 a or third pad 344 ofthe chip 500 b in a wire-bonding process. Similarly, the metal wire 640b has one end that connected to the first pad 312 a or third pad 344 ofthe chip 500 b and has the other end that connected to the first pad 312a or the third pad 344 of the chip 500 c via a wire-bonding process. Themetal wire 640 c has one end that connected to the first pad 312 a orthird pad 344 of the chip 500 c and has the other end that connected tothe first pad 312 a or the third pad 344 of the chip 500 d via awire-bonding process. The metal wire 640 d has one end connected to thefirst pad 312 a or third pad 344 of the chip 500 a and has the other endconnected to the inner leads 610 in a wire-bonding process. In this way,the chips 500 a, 500 b, 500 c and 500 d are electrically connected tothe leadframe 600 when the wire-bonding processes of the metal wires 640a, 640 b, 640 c, and 640 d are completed, wherein these metal wires 640can be gold made wires.

Moreover, the leadframe 600 is provided with bus bar 630 as transferringpad for electrical connections such as power connections, groundconnections, or signal connections. For example, when the bus bar 630 isserved as transferring pad for electrical connection, the metal wire 640e has its one end connected to a pad (pad with letter “b′” for example)of the chip 500 a and has its other end connected to a bus bar (the busbar 6302 for example), and the metal wire 640 h has its one endconnected to the bus bar 6302 and has its other end connected to one ofthe inner leads (inner lead 6122 for example). Moreover, the uppermostchip 500 d of the structure 50 can further have same pads as the pads312 and 344 on the other side such as the arrangement shown in FIGS. 2Dand 5B. Therefore, on the other side of chip 500 d, a plurality of metalwires 640 f are used to connect the chip 500 d (pad with letter “a” forexample) and the inner leads 610 (inner lead 6102 for example), while ametal wire 640 g has its one end connected to a pad (pad with letter “b”for example) of chip 500 d and the other end connected to a bus bar (busbar 6301 for example) and a metal wire 640 i is used to connect the busbar 6301 and one of the inner leads (inner lead 6103 for example).

It is to be noted that the chip 500 b is stacked on and adhered to thearea outside the bonding area 320 of the chip 500 a via a polymermaterial made adhesive layer. However, the wire-bonding sequence of themetal wires 640 is not limited herein, which means it is also allowableto first bond the uppermost chip 500 d and finally bond the lowermostchip 500 a and then connect the chip 500 a with the leadframe 600.

Referring to FIG. 10, which is a cross-sectional view of anotherembodiment of offset chip-stacked package structure in FIG. 6A drawnalong section line A-A or in FIG. 7A drawn along section line B-B. Asshown in FIG. 10, the leadframe 600 and the offset chip-stackedstructure 50 are connected with a plurality of metal wires 640, whereinthe leadframe 600 is composed of a plurality of inner leads 610 arrangedin rows facing each other, a plurality of outer leads (not shown), and adie pad 620. The die pad 620 is provided between the plurality of innerleads 610 and is vertically distant from the plurality of inner leads610, at least a bus bar 630 being provided between the inner leads 610and the die pad 620. In the present embodiment, the bus bar 630 and theinner leads 610 are vertically at the same height. After the offsetchip-stacked structure 50 and the leadframe 600 are connected, the wirebonding process between the leadframe 600 and the offset chip-stackedstructure 50 is then performed. The process of connecting the leadframe600 and the offset chip-stacked structure 50 with metal wires 640 is thesame as what is described above and would not be given unnecessarydetail. Meanwhile, the leadframe 600 in the present embodiment isprovided with bus bar 630 which can be used for electrical connectionssuch as power connections, ground connections or signal connections viathe connection of metal wires 640.

Then, referring to FIG. 11, which is a cross-sectional view of anotherembodiment of offset chip-stacked package structure in FIG. 6A whichdrawn along section line A-A or in FIG. 7A which drawn along sectionline B-B. The only difference between the leadframe and the offsetchip-stacked structure 50 in FIG. 11 and those in FIGS. 9 and 10 is thatthe bus bar 630 is vertically at different heights, wherein the bus bar630 in FIG. 11 is provided between the inner leads 610 and the die pad620 of leadframe 600, the bus bar 630 being vertically distant from theinner leads 610 and the die pad 620. Similarly, after the offsetchip-stacked structure 50 and the leadframe 600 are connected, the wirebonding process of metal wires 640 between the leadframe 600 and theoffset chip-stacked structure 50 is then performed. The process ofconnecting the leadframe 600 and the offset chip-stacked structure 50with metal wires 640 is the same as what is described above and wouldnot be given unnecessary detail. Meanwhile, the leadframe 600 in thepresent embodiment is provided with bus bar 630 which can be used forelectrical connections such as power connections, ground connections orsignal connections.

Then, referring to FIG. 12, which is a cross-sectional view of stillanother embodiment of offset chip-stacked package structure in FIG. 6Adrawn along section line A-A or in FIG. 7A drawn along section line B-B.The leadframe 600 in the present embodiment is composed of a pluralityof inner leads 610 arranged in rows facing each other, a plurality ofouter leads (not shown), and a die pad 620. The die pad 620 is providedbetween the plurality of inner leads 610 and is vertically at the sameheight as the plurality of inner leads 610, at least a bus bar 630 beingprovided between the inner leads 610 and the die pad 620. The bus bar630 is vertically distant from the inner leads 610 and the die pad 620.Similarly, after the offset chip-stacked structure 50 and the leadframe600 are connected, the wire bonding process of metal wires 640 betweenthe leadframe 600 and the offset chip-stacked structure 50 is thenperformed. The process of connecting the leadframe 600 and the offsetchip-stacked structure 50 with metal wires 640 is the same as what isdescribed above and would not be given unnecessary detail. Meanwhile,the leadframe 600 in the present embodiment is provided with bus bar 630which can be used for electrical connections such as power connections,ground connections or signal connections.

As described in the above embodiments, the number of the chips of thechip-stacked structure 50 is not limited, and any skilled in the artcould manufacture a chip-stacked structure including at least threechips according to the above-disclosed method. Meanwhile, the directiontoward which the offset of each chip occurs in forming the structure 50is not so limited by the above-disclosed embodiments. The chip-stackedstructure can be formed with each chip having an offset toward thedirection opposite to the original one disclosed in the aboveembodiments, as shown in FIG. 13. Referring to FIG. 13, the connectionmethod for the chips of the structure 70 and the wire-bonding method forthe chips and the leadframe are similar to that disclosed in theabove-mentioned embodiments and would not be given unnecessary detailsherein.

Moreover, the present invention proposes a combination structure inwhich two offset chip-stacked structure with chips of each structurebeing offset toward opposite directions are combined together. Anexample of such is shown in FIG. 14. Referring to FIG. 14, thestructures 50 and 70 are provided together on a die pad 620 of aleadframe 600. The connection method for the chips of the structures 70and 50 and the wire-bonding method for the chips and the leadframe aresimilar to that disclosed in the above-mentioned embodiments and wouldnot be given unnecessary details herein. Moreover, the leadframe 600 inthe present embodiment is provided with bus bar 630 as transferring padfor electrical connections such as power connections, groundconnections, or signal connections. It is to be noted that theconfiguration and the number of the bus bar 630 here are examples onlyand do not limit the structure and the number of bus bar 630 whendifferent circuit designs are considered.

While the invention has been described by way of examples and in termsof the preferred embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements aswould be apparent to those skilled in the art. Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A chip-stacked package structure with leadframe having bus bar,comprising: a leadframe, composed of a plurality of inner leads arrangedin rows facing each other, a plurality of outer leads, and a die pad,wherein said die pad is provided between said plurality of inner leadsarranged in rows facing each other; a plurality of offset chip-stackedstructures set on said die pad and electrically connected to saidplurality of inner leads arranged in rows facing each other; and anencapsulant, covering said plurality of offset chip-stacked structuresand said leadframe, said plurality of outer leads extending out of saidencapsulant; wherein said leadframe comprises at least a bus barprovided between said plurality of inner leads arranged in rows facingeach other and said die pad, and said bus bar is vertically distant fromsaid plurality of inner leads and said die pad.
 2. The chip-stackedpackage structure according to claim 1, wherein said bus bar is arrangedin a ring-shaped configuration.
 3. The chip-stacked package structureaccording to claim 1, wherein said bus bar is arranged in astripe-shaped configuration.
 4. The chip-stacked package structureaccording to claim 1, wherein said plurality of offset chip-stackedstructure is selectively electrically connected to part of said bus bar.5. The chip-stacked package structure according to claim 1, wherein saidbus bar be used for electrical connections such as power connections,ground connections, or signal connections.
 6. The chip-stacked packagestructure according to claim 1, wherein said plurality of chips formingsaid offset chip-stacked structure has the same size.
 7. Thechip-stacked package structure according to claim 1, wherein saidplurality of chips forming said offset chip-stacked structure comprise aplurality of first chips having the same size and at least a second chiphaving size different from that of said first chips.
 8. The chip-stackedpackage structure according to claim 1, wherein said plurality of chipsforming said offset chip-stacked structure are misaligned to form offsetstacking.
 9. The chip-stacked package structure according to claim 1,wherein said plurality of offset chip-stacked structures comprise afirst offset chip-stacked structure and a second offset chip-stackedstructure, and said two offset chip-stacked structures with chips ofeach structure being offset toward opposite directions.
 10. Achip-stacked package structure with leadframe having bus bar,comprising: a leadframe, composed of a plurality of inner leads arrangedin rows facing each other, a plurality of outer leads, and a die pad,wherein said die pad is provided between said plurality of inner leadsarranged in rows facing each other; a plurality of offset chip-stackedstructures set on said die pad and electrically connected to saidplurality of inner leads arranged in rows facing each other, whereineach of said offset chip-stacked structure comprises: a chip bodyprovided with a bonding area, said bonding area being adjacent to oneside edge or two neighboring side edges of said chip, wherein said chipis provided with a plurality of first pads in said bonding area and aplurality of second pads outside said bonding area; a first passivationlayer provided on said chip, wherein said first passivation layer isprovided with a plurality of first openings for exposing said pluralityof first pads and said plurality of second pads; a redistribution layerformed with a plurality of third pads inside said bonding area, whereinsaid redistribution layer is provided on said first passivation layerfor establishing connection between said plurality of second pads andsaid third pads; and a second passivation layer covering saidredistribution layer, wherein said second passivation layer has aplurality of second openings for exposing said plurality of first padsand said plurality of third pads; an encapsulant, covering saidplurality of offset chip-stacked structures and said leadframe, saidplurality of outer leads extending out of said encapsulant; wherein saidleadframe comprises at least a bus bar provided between said pluralityof inner leads arranged in rows facing each other and said die pad, andsaid bus bar is vertically distant from said plurality of inner leadsand said die pad.
 11. The chip-stacked package structure according toclaim 10, wherein said redistribution layer is made up of gold, copper,nickel, titanium tungsten, titanium or others.
 12. The chip-stackedpackage structure according to claim 10, wherein said plurality of firstpads and said plurality of third pads of said plurality of chipstructures are arranged in at least one row along a side edge of thechip.